Properties of traps determined from the optical quenching of luminescence and dielectric losses in ZnS:Cu

Abstract

Measurements of dielectric losses in ZnS: Cu single crystals illuminated by uv light have been made by means of a high sensitive microwave apparatus. The quenching of dielectric losses by visible light in ZnS: Cu single crystals as a function of wavelength (optical quenching spectrum) has been measured at room temperature in the range 0.4 to 0.8 μm. Moreover, a series of simultaneous measurements of luminescence and dielectric losses using as a source of quenching light an mW He‐Ne laser are reported in order to test some proposed models for the mechanism of optical quenching. A satisfactory account for the present results is obtained in terms of non‐radiative recombinations between trapped electrons and free holes in the valence band. The kinetic of these recombinations is not the same if the quenching light is applied after or in addition to the uv excitation. The results show also that the dielectric behaviour of shallow and deep traps is different.